Drill jig

ABSTRACT

A drill jig for making a channel in a timber for containing flowable preservative comprises a body (10) having a first or perpendicular guide bore (20), a second or oblique guide bore (22) and a third or vertical guide bore (24). The guide bores (22) and (24) intersect in a cylindrical locating spigot (18) and the axes of the guide bores (20) and (22) intersect in the timber to be drilled. A collet (26) on the shank of the drill bit (28) limits the depth of penetration by the lower face (32) of the collet abutting an abutment face (34) on the body (10). The depth of pentration when using the guide bore (20) or (24) is limited by the collet (26) coming into abutment with an adjustable stop (38) on the body (10). No adjustments are necessary as between drilling perpendicular or oblique bores and it is ensured that the bores formed in the timber intersect to form a continuous channel for receiving flowable preservative.

DESCRIPTION

The present invention relates to timber preservation and more particularly to a drill jig to assist in drilling intersecting bores in timber to form a channel to receive and retain a timber preservative.

In my U.K. Patent Specification No. 2113282 A published Aug. 3, 1983, there is described a method of treating a wooden frame, such as a window frame, with a preservative, in which the members making up the frame are drilled from a surface of the members at pre-determined localities along the length thereof to form bores, at least some of which are angled so that the bores intersect to form a channel, and in which a fluid preservative is introduced into the channel which is thereafter closed off. In my U.K. Patent Specification No. 21 30936A published June 13, 1984, there is described a drill jig for drilling the bores in the timber, which drill jig comprises a body formed with an inclined guide bore and having a locating spigot adapted to be received in a bore formed in the timber to be drilled.

The use of the drill jig described in the said U.K. Patent Specification No. 2130936A entails a series of blind locating bores being formed beforehand in the length of timber to be drilled and the drill jig being angularly located in an exact position with the cylindrical spigot located in one of the blind locating bores so that the drill bit then inserted through the guide bore to drill a hole which intersects a hole previously drilled. The need to carefully position the jig so that the bores do intersect makes the whole operation slow and hazardous in as much as, if the bores do not intersect, then a continuous channel which can be filled with preservative is not formed.

It is an object of the present invention to provide a drill jig which enables several holes to be drilled in the timber such that the holes will always intersect.

It is another object of the present invention to provide such a drill jig which can be used for drilling both oblique holes and substantially perpendicular holes such that the depth of penetration of the drill into the timber is limited by means of adjustable stops and such that the bores intersect and are drilled to substantially the same depth within the timber despite the inclined bores being longer than the substantially perpendicular bores and without having to make any adjustments as between drilling the inclined bores and drilling the substantially perpendicular bores.

A drill jig according to the present invention comprises a body having a base surface adapted to be placed against a face of a length of timber to be drilled, locating means for locating said body on said timber face, said body having first and second drill guide bores therethrough, said first guide bore being perpendicular to said base surface or at least approximately so and said second guide bore being at an acute angle to said first guide bore such that the axis of the guide bores intersect in the timber to be drilled, a depth stop adapted to be attached adjustably to a drill or to a drill bit so as to limit the depth of penetration of the drill bit, when received in said second guide bore, by said depth stop coming into abutment with an abutment face on said body, and an adjustable abutment disposed on the body so as to be abutted by said depth stop when said drill bit is received in said first guide bore, to limit the depth of penetration.

Conveniently the locating means comprises a locating spigot on said body and projecting from said base surface so as to be received in a locating bore formed in said timber face. The locating spigot is preferably cylindrical so that the drill jig can be disposed at any desired angular position on the length of timber and in particular can be disposed at two substantially diametrically opposed angular positions to enable two sets of bores to be drilled from the same locating bore. To this end it is advantageous for the second oblique guide bore to pass through the spigot.

To increase the number of holes which can be drilled using the drill jig, it is preferable for the body to have a third guide bore which is substantially perpendicular to said base surface, the axis of the second and third guide bores intersecting and the first, second and third guide bores being substantially co-planar. It is convenient for the adjustable abutment to be so disposed on the body, e.g. mid-way between the first and third guide bores, such that the adjustable depth stop comes into abutment with the adjustable abutment where the drill bit is received in the first guide bore or the third guide bore.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a simplified perspective view of a window frame incorporating cavities in accordance with the present invention;

FIG. 2 is a perspective view of part of a window frame showing the location of interconnecting bore holes forming a channel in the frame;

FIG. 3 is a perspective view of part of a window frame showing the location of bore holes according to another embodiment of the invention;

FIG. 4 is a section through a timber member showing one arrangement for forming and plugging the bore holes;

FIG. 5 is a perspective view of a drill jig according to the invention; and

FIG. 6 is a side elevation through a frame member being drilled using the jig of FIG. 5.

Referring to the drawings, there is shown a wooden window frame 1 having two vertical stiles 3 interconnected by horizontal top and bottom rails 5. The frame is divided into four by an intermediate vertical mullion 7 and a horizontal transom 9 which intersect at 11. The bottom rail 5 forms a cill. Each of the lengths of timber 3, 5, 7 and 9 has therein a longitudinally extending cavity or closed channel 15 (indicated by dotted lines in FIG. 1). The channels 15 are interconnected by various means described further hereinafter. A closeable orifice 17 in communication with the channel 15 is provided at any convenient location in the frame. A bleed port 19 may be provided in the channel 15 at the highest point thereof. The arrangement is such that wood preservatives may be injected into the closed channel 15 by way of the closeable orifice 17 so as to fill the interconnecting channels 15 and penetrate the wood. The wood preservative is preferably injected under pressure at say, 100 p.s.i. (7.8 bar). The closeable orifice 17 is formed by a non-return ball valve which is screwed into a threaded hole (say 10 mm diameter), formed in the timber. The preservative is absorbed in a direction from the inside out. Thus periodic treatment can be carried out without disturbing any external coating on the wood.

In the embodiment, illustrated in FIGS. 2, 3 and 4, the continuously extending cavity is formed in wooden members 3, 5 of a window frame by a plurality of bores 120 which are drilled into the wood at an angle, so that adjacent bores intersect. Part of a frame is shown in FIG. 2 with the interconnecting bores shown by the dotted lines. The bores 120 are drilled from any convenient face of the wood frame, and each bore hole 122 is filled with a plug 124 which is preferably glued in position. A hot melt adhesive may be employed. In the arrangement shown in FIG. 4 two plugs are employed. A first plug 124 is inserted into the bore hole 122 and a second bore 125 drilled perpendicularly to the face of the timber receives a second plug 126. Glue is introduced behind the plug 124, and the second plug is finished flush with surface of the wood. The second plug is approximately 12 mm in length and cut across the grain.

The bores 120 of adjacent members of the frame are arranged to connect where the members 3 and 5 are joined together so that a frame can be treated from one filler point 128. The filler point is connected to the bores 120 by way of a bore 129 provided with a filled adaptor. Alternatively, one of the openings 122 of the bores 120 may be fitted with the filler adaptor.

The adaptor can comprise a nipple which can be screwed into the wood to align with the bore 129. A tube or other connecting means may be fitted to the nipple to permit preservative to be introduced into the cavity from a suitable applicator. This may be done under a pressure of up to 100 p.s.i. (7.8 bar) as previously described. In one embodiment, once the cavities have been filled, and where necessary, the fluid allowed to penetrate into the wood under pressure, the filler adaptor is removed and a threaded blanking plug 130 screwed in position in place of it. The blanking plug is preferably a plastic, such as nylon. As an alternative, a spring-loaded non-return valve may be employed as the filler adaptor and blanking plug.

The bores 120 can be formed at any convenient angle and the overlap between adjacent bores can be varied. The more the adjacent bores overlap then the better the treatment of wood, since more holes would be required for a given length of wood. The adjacent bores may be commenced from the same surface bore, i.e. without overlap.

Typically the bores 120 are 6 mm diameter and the filler hole 129, 10 mm diameter. Only one filler hole is needed and a vent hole is not necessary when the preservative is injected under pressure.

After the channels, i.e. bores, 120 have been drilled they are preferably cleaned out using compressed air. With the bore openings 122 blocked off, the system can be tested for leaks etc. using air pressure.

Where it is required to inject wood preservative into a timber structure, such as a window frame, door frame or the like, which already has the internal channel-ways, the liquid is introduced from a commercial dispenser and delivered under minimum pressure or controlled pressure via a non-return valve of the dispenser and an adaptor and nozzle which connects with the orifice 17 in the timber. The orifice has a threaded portion for connection with the nozzle of the dispenser. Alternatively, the nozzle may be received in the orifice as a tapered fit. The liquid is injected so as to fill to capacity all the interconnecting channels beneath the surface of the timber frame. The applicator is then removed thus leaving the injected fluid concealed within the timber members where it will, in due course, permeate through and across the grain of the entire frame. Further fluid may be injected at convenient intervals, thus ensuring the preservation of the timber for a lengthy and indefinite period.

The channels in each member may be arranged to connect with one another at the joints between the bars making up the frame. Alternatively, separate channels for each member of the frame may be provided.

Where there is a possibility of excessive seepage via ill fitting joints caused by incorrect manufacture or consequent warping or shrinkage of timber, it may be desirable to isolate the corner joints from the channel. Thus, the channel would terminate adjacent the corner joint in which case the channel would not be a continuous cavity round the entire frame.

Clearly it can be seen that, if undue seepage of fluid via ill fitting joints or misplaced nail holes, or knot holes etc., etc. did occur, then the specific and offending section could be isolated, thus receiving its quota of preservative fluid on a strictly controlled basis.

When it is required to inject wood preservative into a timber structure, such as a window frame, door frame or the like, which already has the internal channel-ways, the liquid is introduced from a commercial dispenser and delivered under controlled pressure via a non-return valve of the dispenser and via a pressure chamber into the channel of the frame until pressure is seen to build up. At that point air from the compressor is introduced at 100 p.s.i. (7.8 bar) and maintained for a period of three minutes or until traces of preservative are seen to be exuding from the frame. The multi nozzle connectors which fit into the orifice 128 in the timber have a threaded portion for connection with the nozzles of the pressure chamber. Alternatively, on a different model a single nozzle may be received into the orifice as a tapered fit. The liquid is injected so as to fill to caphis invention is to improve the data compression ratio by utilizing the system of the type described above, thereby to save the memory of the character image data and result in cost reduction.

The conventional run-length method is based on the coding of the uniform character image on the basis of the length N of a character image segment and the length M of a background portion in advance of the segment. The conventional two-dimensional difference method is based on the coding of the character image in accordance with the difference amount between positions of the start and final points of each segment in the two sequential lines.

On the other hand, the compression system according to this invention is characterized by the steps of comparing data of the previous line and present line, discriminating contact mode in a row direction of a character image segment existing in the lines, and obtaining compression data which is prepared by coded modes different in each segment in accordance with the result of the discrimination.

According to this invention, generation, deletion, and contact modes of each segment existing in an optional line could be specified even with respect to a "kanji" having complicated composition by properly combining six kinds of the following segment contact modes, the segment contact modes being:

(1) Insertion Mode (INS)

Where no segment contacting to one segment in the present line exists in the previous line.

(2) Simple Contact (Difference) Mode (DIF)

Where one segment in the previous line contacts to one segment in the present line.

(3) Join Mode (JOIN)

Where a plurality of segments in the previous line contact to one segment in the present line.

(4) Fork Mode (FORK)

Where one segment in the previous line contacts to a plurality of segments in the present line.

(5) Join-Fork Mode (J-F)

Where a plurality of segments in the previous line contact to a plurality of segments in the present line.

(6) Deletion Mode (DEL)

Where no segment contacting to one segment in the previous line exists in the present line.

In addition, according to this invention, the shape of an optional character image could be completely specified by commonly using the six contact modes described above and auxiliary modes such as an end of line and new line mode (EOL) and an end of file mode (EOF) which are not directly related to the generation, disintegration and contact modes of the segments.

Among the auxiliary modes, the EOL, which will be described in detail hereinafter, corresponds to a case where a new segment corresponding to the INS exists and the EOF corresponds to a case where the character image data finishes.

According to the system of this invention different types of information can be encoded respectively in response to the aforementioned modes, and therefore, character data composed of complexed segments can be effectively compressed by outputting the encoded data incidentally to a control code prescribing the contact modes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing one example of character data which is typically bit-exploded in matrix type;

FIGS. 2A through 2I show types of informations to be encoded with respect to respective contact modes;

FIGS. 3A and 3B show examples of code formats;

FIG. 4 is a schematic view showing one example of composition for obtaining coded data according to the compression system of this invention; and

FIGS. 5A and 5B are views showing comparison of an actual coded data obtained by the system of this invention with a concrete figure.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 2 typically shows concrete contents of the respective modes and types of information to be encoded and in FIG. 2 one segment is formed by each rectangular block in one line. Further, FIG. 3A and FIG. 3B are diagrams showing examples of a preferred code format to encode these informations. As shown in FIG. 3, the code format comprises control codes consisting of 4 bits (X₀, X₁, X₂, X₃) arranged to discriminate the aforesaid various modes and data codes having variable lengths succeeding to the control codes.

The actual contents and types of the information to be actually encoded and one example of code format will be described hereinbelow in conjunction with FIGS. 2 and 3.

{INSERTION MODE (INS)}

In a case where, such as regarding a segment 2 shown in FIG. 2A, a corresponding contact segment does not exist in the previous line and a new segment is generated and inserted there, information is encoded regarding (1) the length M of a background portion preceding the segment (i.e. length M from the end of the line L in case of no preceding segment) and (2) information regarding the length N of the segment.

In this processing in order to control diffuseness of a data code to be encoded, it is desired to classify the INS into either one of respectively different insertion mode (INS-1) or (INS-2) in response to the length N of the segment (for example, in response to a time when N is below "63" which can be expressed by 6 bits, or over "64" which can be expressed by 7 bits.) In FIG. 3A, there is shown one example of code format of the information coded by the aforesaid insertion mode (INS) as control code (INS-1) or (INS-2).

{SIMPLE CONTACT (DIFFERENCE) MODE (DIF)}

In a case where, such as regarding respective segments shown in FIG. 2B through FIG. 2E, one segment in the previous line contacts to only one segment in the present line in a row direction, the DIF is classified into the following four modes in response to value difference amounts (S;D) at bilaterial both ends of each contact segment.

(1) [Difference 0 Mode (DIF-0)] FIG. 2B

Where both of the difference amounts (S;D) are "0".

(2) [Difference 1 Mode (DIF-1)] FIG. 20, left half

Where both of the difference amounts (S;D) are below "1".

(3) [Difference 3 Mode (DIF-3)] FIG. 2C, right half FIG. 2E

Where both of the difference amounts (S;D) are below "3".

(4) [Difference 4 Mode (DIF-4)] FIG. 2D

Where one of the difference amounts (S;D) is over "4".

In the case of [Difference 0 Mode (DIF-0)], as shown in FIG. 2B, only the information regarding repeat number (K) of the Difference 0 Mode in the succeeding lines is encoded. In FIG. 3B, there is shown one example of code format of the information coded by the Difference 0 Mode as control code (DIF-0).

In either one of the cases of [Difference 1 Mode (DIF-1)] or [Difference 3 Mode (DIF-3)], as shown in FIG. 2C, the information is encoded regarding the repeat number (K) of the difference mode in the succeeding line and difference amounts (SK;Dk) of the respective following segment corresponding to the repeat number (K) and the polarity information (Ps;Pd) of the difference amounts (Sk;Dk).

In this case, it can be facilitated to delete the diffuseness of the data to be encoded by applying only the polarity information of one type regarding the K number of the difference amounts (Sk;Dk) by taking into consideration such a characteristic as the fact that the shape of the character image has a continuous inclination in a certain interval.

In FIG. 3, there is shown one example of code format of the information coded by the Difference 1 Mode or Difference 3 Mode as control code (DIF-1) or (DIF-3).

In the case of [Difference 4 Mode (DIF-4)], as shown in FIG. 2D, are encoded in every segment the information regarding the difference amounts (S;D) and the polarity information (Ps;Pd) thereof.

However, in the case of [Difference 4 Mode (DIF-4)], as further shown in FIG. 2D, it is classified into [Difference 4A Mode (DIF-4A)], [Difference 4B Mode (DIF-4B)], and [Difference 4C Mode (DIF-4C)] in accordance with cases where the difference amounts (S;D) are below "7", between "8-15", and over "16", respectively. There is shown in FIG. 3A, one example of the information coded by Difference 4 Mode as control code (DIF-4A), (DIF-4B) or (DIF-4C).

When the data of the aforementioned [Simple Contact (Difference) Mode (DIF)] is encoded, precedence order of the respective difference modes is basically set as follows.

[Difference 0 Mode]>[Difference 1 Mode]>[Difference 3 Mode]>[Difference 4A Mode]>[Difference 4B Mode]>[Difference 4C Mode].

However, this precedence order is not absolute and in cases where the difference amounts (S;D) are satisfied with a condition of below "3" (including "0", "1", and "2"), some extent of the diffuseness of the data code to be encoded will be deleted and the data compression ratio will be improved by selecting either one of [Difference 0 Mode], [Difference 1 Mode] or [Difference 3 Mode] in accordance with generating condition of segments in the succeeding lines of the aforementioned mode.

For example, in a case as shown in FIG. 2E, a plurality of segments can be synthesized as one mode and dealt with, in spite of the fact that the difference amounts (S;D) of lines up to the fourth line are "0" or "1" by dealing it with as the [Difference 3 Mode] of the type described above.

{JOIN MODE (JOIN)}

There is shown in FIG. 3B, one example of the information coded by the join mode as control code name (JOIN).

As shown in FIG. 2F, in a case that a plurality of segments in the previous line contact to one segment in the present line, are encoded the information regarding the number of segments (Q) to be joined and the difference amounts (S;D) between the most outward bilateral ends of a plurality of segments to be joined and the bilateral ends of one joined segment and polarity information (Ps;Pd) of the difference amount (S;D).

{FORK MODE (FORK)}

There is shown in FIG. 3B, one example of the information coded by the fork mode as control code name (FORK).

As shown in FIG. 2G, in a case where one segment in the previous line contacts to a plurality of segments in the present line, information regarding the forked segment number (Q), and the run-lengths (mq;Nq) of the respective forked segments is encoded.

{JOIN-FORK MODE (J-F)}

There is shown in FIG. 3B, one example of the information coded by the Join-Fork mode as control code name (J-F).

As shown in FIG. 2H, in a case that a plurality of segments in the previous line contact to a plurlaity of segments in the present line, information regarding the jointed segment number (Qj), the forked segment number (Qf), and the run-lengths (Mqf;Nqf) of the respective forked segments is encoded.

{END OF LINE AND NEW LINE MODE (EOL)}

As shown in FIG. 2I, in a case that there exists a new second segment in which the most righthand segments in lines after the present line correspond to the insertion mode (INS) with respect to the first segment corresponding to the insertion mode (INS), the information K pertains to the number of new lines from the first segment to the second segment. In this case, the upper and lower ends of the data matrix in the row direction are considered as the start and final lines, respectively.

{DELETION MODE (DEL)} OR {END OF FILE MODE (EOF)}

There is shown in FIG. 3B, one example of the information coded by the end of line and new line mode as control code name (EOL).

In a case where no contact segment exists in the present line or where character image data finishes, only the deletion mode (DEL) control code or the end of file mode (EOF) control code is outputted.

Types of the information encoded in response to the discriminated modes and relationship between the information and the character image data have been described hereinabove in conjunction with FIG. 2.

In this case, the join-fork segment number (Q) which can be treated as data can be increased substantially by "2".

FIG. 4 is a schematic view showing example of a system for requiring coded data as described above.

Referring to FIG. 4, reference numeral 41 designates a scanner device for obtaining binary data from a matrix image corresponding to a two-dimensional character image and the scanner device 41 operates, for example, in such a manner that transmitted light or reflected light from a character image pattern 43 irradiated by scanning light from a flying-spot tube 42 is detected by a detector 44 and the desired binary data is obtained by shape-sampling a signal from the detector 44 representing the detected light.

The binary data obtained by the scanner device 41 can be temporarily memorized by a memory device 45.

Reference numeral 46 designates an operation control unit which performs data processing of the binary data supplied by online or batch processing and outputs required coded data to a compression data memory 47, usually, the operation control unit 46 being preferably composed of an electronic computer.

Main processing order in the operation control unit 46 is as follows:

(1) To input the original binary data;

(2) To extract the segments and compare lines;

(3) To detect the contact modes of the segments;

(4) To check optimization of the respective contact modes;

(5) To decide the most suitable contact mode;

(6) To operate desired information regarding the decided contact mode;

(7) To encode the operated information; and

(8) To output the encoded data.

FIGS. 5A and 5B show an actual example of an encoded data obtained by the processing order described above according to the system of this invention in comparison with concrete figures each consisting of a image element of 25×25.

The character image data compression system according to this invention was inspected by applying it to an optionally selected 56 types of "kanji" and data compression ratio of 18.1% was obtained with respect to 100×100 image element per one character. Moreover, this proves that data compression ratio of 39.5% is obtained by applying the system of this invention to a different method under the same conditions as set forth above.

As described in detail hereinbefore, the character image data compression system of this invention in which binary data of matrix type corresponding to a two-dimensional character image is compressed is basically characterized by the steps of confirming existance of a character image segment in every data of each line direction, comparing the data of adjacent two sequential lines, i.e. previous line and present line, in the case of the existence of the character image segment, discriminating a contact mode in a row direction of the character image segment, and outputting, in response to the result of this discrimination, variable coded data regarding information of respectively different types incidentally to a control code prescribing the contact mode.

As described in the foregoing, this invention makes it possible to optionally output the coded data in conformity with the characteristic of a character image having complicated composition, typically, such as "kanji", thereby to improve the data compression ratio as a whole character and to make compact the capacity of a character data memory. 

What is claimed is:
 1. A character image data compression method for compressing matrix-type binary data having data elements formed in lines and in combination corresponding to a two-directional character image comprising the steps of:detecting the occurrence or non-occurrence of a character image segment in each data element of the matrix in each line; identifying a contact state in a vertical direction of said character image segment, by comparison of data in adjacent lines; and producing an output comprising a control code corresponding to said contact state, and variable length coded data corresponding to information of respectively different types in accordance with the type of contact state, said control code being applicable to all of said states, wherein the contact state in a vertical direction of said character image segment, is identified as any one of the following modes: an insertion mode (INS) in which no contact segment exists in a previous line, a simple contact different mode (DIF) in which one segment in the previous line contacts to one segment in a present line, a join mode (JOIN) in which a plurality of segments in the previous line contact to one segment in the present line, a fork mode (FORK) in which one segment in the previous line contacts to a plurality of segments in the present line, a join-fork mode (J-F) in which a plurality of segments in the previous line contact to a plurality of segments in the present line, and a deletion mode (DEL) in which no contact segment exists in the present line, and the encoded information includes a control code corresponding to the contact state, and also(a) information regarding a length (M) of a background portion prior to said segment and a length (N) of said segment in a case where said contact state corresponds to the insertion mode (INS), (b) information regarding difference amounts (S;D) at each end of respective contact segments and/or repeat number (K) of said simple contact difference mode of the succeeding lines, and/or polarity information (Ps;Pd) applying positive and negative polarities to said difference amounts (S;D) in a case where said contact state corresponds to the simple contact difference mode (DIF), (c) information regarding a number (Q) of segments to be joined and difference amounts (S;D) between extreme ends of a plurality of segments to be joined and ends of one joined segment, and polarity information (Ps;Pd) regarding said difference amounts (S;D) in a case where said contact state corresponds to the join mode (JOIN), (d) information regarding a number (Q) of forked segments and run-lengths (Mq;Nq) of formed segments in a case where said contact state corresponds to the fork mode (FORK), or (e) information regarding a number (Qj) of segments to be joined, the number (Qf) of the forked segments, and run-lengths (Mqf;Nqf) of said forked segments in a case where said contact state corresponds to join-fork mode (J-F), but when the contact state corresponds to the deletion mode, onlly a deletion mode control code (DEL) is produced.
 2. An image-data compression method according to claim 1, in which, when the said contact state corresponds to the insertion mode (INS), insertion mode control codes different from one another are produced in accordance with the length N of said segment and one of two insertion mode control codes or may be produced in accordance with a case where said length N of the segment is below "63" or where said length of the segment is over "64".
 3. An image data compression method according to claim 1, wherein a case where said discriminated result of said contact state corresponds to the simple contact difference mode (DIF), difference mode control codes different from one another are outputted in accordance with said difference amounts (S;D).
 4. An image data compression method according to claim 3, wherein, in the case where said difference amounts (S;D) are both "0", only a difference 0 mode control code is produced together with coded data regarding repeat number (K) of said simple contact difference mode in the succeeding lines.
 5. An image data compression method according to claim 3, wherein the case where said difference amounts (S;D) are both "1" or less, or "3" or less, a difference mode control code or (DIF-1) or (DIF-3) is produced together with coded data regarding information of repeat number (K) of said simple contact difference mode in succeeding lines and difference amounts (Sk;Dk) of respective segments in the succeeding lines corresponding to said repeat number (K) and polarity information (Ps;Pd) of said difference amounts (Sk;Dk), and only one type of said polarity information (Ps;Pd) is applied commonly to said difference amounts (Sk;Dk) of said segment in the succeeding lines.
 6. An image data compression method according to claim 3, wherein in the case where either of said difference amounts (S;D) is "4" or more, a difference mode control code is produced together with coded data regarding information of said difference amounts (S;D) and polarity information (Ps;Pd) of said difference amounts (S;D).
 7. An image data compression method according to claim 6, wherein control codes different from one another are produced in accordance with values of said difference amounts (S;D) and any one of "difference 4" mode control codes, and is produced in accordance with any one of cases where said difference amounts (S;D) are "7" or less, "8-15", or "16" or more.
 8. An image data compression method according to claim 1, wherein in a case where said contact state corresponds to the simple contact difference mode satisfying a condition that said difference amounts (S;D) are both "3" or less, any one of difference mode control codes, and is selected in accordance with a condition of generation of the contact state satisfying said difference amount condition in the following line and the selected control code is produced together with said coded data coincident with said selected control code.
 9. An image data compression method according to claim 1, in which in a case where said contact state corresponds to any one of said join mode, said fork mode, and said join-fork mode, there is coded a value obtained by substracting "2" from the number of segments to be actually joined or forked. 